Microstructure and High-Temperature Tribological Properties of Nickel-Based Composite Coatings with Laser In Situ Induced TiC and MoSi2 Reinforcement

In order to improve the tribological properties of Inconel 718 alloy at elevated temperature, nickel-based composite coatings with in situ TiC and MoSi₂ reinforcement were deposited onto Inconel 718 alloy via laser cladding the complex Hastelloy C276 alloy and Ti₃SiC₂ powder in this study. The influences of the in situ TiC and MoSi₂ reinforcement from the complete decomposition of Ti₃SiC₂ powders on the microstructure, mechanical and tribological properties of prepared coatings were systematically investigated. These coatings exhibited a microstructure consisting of coarse γ-Ni dendrites, slender interdendritic MoSi₂ phases, and TiC ellipsoidal particles. The inclusion of an appropriate amount of in situ fine TiC and MoSi₂ precipitates significantly inhibited the directional growth and coarsening of γ-Ni dendrites, resulting in improved mechanical properties and wear resistance. Among the three types of coatings applied through laser cladding, the Ni-based composite coating with 20 wt.% Ti₃SiC₂ addition demonstrated relatively high hardness (538.4 HV_0.3) and flexural strength (1651.37 MPa), coupled with a lower mean friction coefficient (0.39) and wear rate (3.16 × 10^–5 mm³/N m) at 30 °C. These TiC and MoSi₂ reinforcements proved effective in reducing cutting stress and resisting plastic deformation, thereby enhancing friction coefficients and wear rates across the temperature range from 30 to 400 °C. The prepared coatings also exhibited promising wear resistance at 800 °C, attributed to the formation of protective tribofilm oxidative layers. However, the breakage of the lubricating tribofilms caused obvious wear damage and exacerbated friction coefficients and wear rates at 1000 °C.